The purpose is to characterize enzyme defects in patients with known or suspected porphyria and their families. Methods include measurement of porphobilinogen deaminase and porphyrins in erythrocytes, porphyrins and porphyrin precursors (deltaaminolevulinic acid and porphobilinogen) in plasma and urine, and porphyrins in feces. Selected patients are entered in other porphyria research protocols at this and other institutions, including analysis of DNA to identify specific mutations in genes for heme biosynthetic pathway enzymes.